title: Complete amino acid sequence and homologies of human erythrocyte membrane protein band 4.2.
abstract: The complete amino acid sequence for human erythrocyte band 4.2 has been derived from the nucleotide sequence of a full-length 2.35-kilobase (kb) cDNA. The 2.35-kb cDNA was isolated from a human reticulocyte cDNA library made in the expression vector lambda gt11. Of the 2348 base pairs (bp), 2073 bp encode 691 amino acids representing 76.9 kDa (the SDS/PAGE molecular mass is 72 kDa). RNA blot analysis of human reticulocyte total RNA gives a message size for band 4.2 of 2.4 kb. The amino acid sequence of band 4.2 has homology with two closely related Ca2(+)-dependent cross-linking proteins, guinea pig liver transglutaminase (protein-glutamine gamma-glutamyltransferase; protein-glutamine: amine gamma-glutamyltransferase, EC 2.3.2.13) (32% identity in a 446-amino acid overlap) and the a subunit of human coagulation factor XIII (27% identity in a 639-amino acid overlap), a transglutaminase that forms intermolecular gamma-glutamyl-epsilon-lysine bonds between fibrin molecules. The region of greatest identity includes a 49-amino acid stretch of band 4.2, which is 69% and 51% identical with guinea pig liver transglutaminase and the a subunit of factor XIII, respectively, within the regions that contain the active sites of these enzymes. Significantly, within the five contiguous consensus residues of the transglutaminase active site, Gly-Gln-Cys-Trp-Val, band 4.2 has an alanine substituted for cysteine (which is apparently essential for activity). Consistent with this active site substitution, erythrocyte membranes or inside-out vesicles, which contain band 4.2, show no evidence of transglutaminase activity by two types of in vitro assay.
authors.affiliation: Department of Biomedical Research, St. Elizabeth's Hospital, Boston, MA.
authors.forename: C
authors.initials: C
authors.lastname: Korsgren
authors.forename: J
authors.initials: J
authors.lastname: Lawler
authors.forename: S
authors.initials: S
authors.lastname: Lambert
authors.forename: D
authors.initials: D
authors.lastname: Speicher
authors.forename: C M
authors.initials: CM
authors.lastname: Cohen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001798:Blood Proteins / Q000235:genetics*; D003598:Cytoskeletal Proteins; D004247:DNA / Q000097:blood / Q000235:genetics; D015723:Gene Library; D006801:Humans; D008565:Membrane Proteins / Q000097:blood / Q000235:genetics; D008969:Molecular Sequence Data; D010957:Plasmids; D015183:Restriction Mapping; D012156:Reticulocytes / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid
chemical_list: D001798:Blood Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; C044791:erythrocyte membrane band 4.2 protein; D004247:DNA